: The long-term objective of this research is to study the development, deterioration, and plasticity of auditory pathways mediating human communication. Specifically, our aim is to examine the development of the central auditory system as reflected by latencies of P1 and Ni cortical auditory evoked potentials in normal-hearing children and in congenitally deaf children after they are fitted with a cochlear implant. Three projects are proposed. The goal of the first project is to provide a comprehensive account of the development of P1 and Ni latencies in normal-hearing children. These data will serve as a baseline against which to compare the performance of cochlear implant recipients. In the second project we will examine whether, and to what extent, pediatric cochlear implant recipients show a delay in the development of P1 and NI latencies. The goal is to determine the age after which cochlear implantation would be in a physiologically degenerate auditory system, or conversely, the age before which implantation would be in a relatively 'normal' auditory system. The third project is a longitudinal assessment of the development of P1 and NI latencies in pediatric implant users. The goal is to determine the time period over which plasticity remains a property of the central auditory pathways. Overall, our experiments are designed to assess the consequences on the developing central auditory system of initiating electrical stimulation at different ages. The results of these experiments could provide an estimate of the upper age limit for implantation into a highly plastic and/or relatively non-degenerate auditory system.